The following United States Letters Patents are representative of the most relevant prior art known to the applicants at the time of filing the application.
______________________________________ 2,836,017 May 27, 1958 R. L. Tygh 3,576,090 April 27, 1981 F. O. Shoemaker 4,240,230 December 23, 1980 S. Ferrantini 4,507,897 April 2, 1985 R. G. Vieau ______________________________________
There are types of grinding wheels which grind on a side surface rather than on the periphery, which is the more usual way to use a grinding wheel. Commonly used wheels of this type are the depressed center wheel of U.S. Pat. No. 4,240,230, the disc wheel of U.S. Pat. No. 3,576,090 and the cylinder wheel of U.S. Pat. No. 4,507,897. The characteristic that all three types of wheels have in common is that they all utilize a rather complicated means of attaching the wheel to the driving means. It is this type of wheel and mounting or attaching means that is the subject matter of the present application.
U.S. Pat. No. 3,576,090, so far as it is relevant to the present invention, disclosures a composite disc wheel 2 made up of a bottom grinding section 4 containing useable abrasive and a back section 6 containing nonabrasive particles or a nonuseable layer of abrasive as it is referred to in the patent. The abrasive in the abrasive section 4 and the nonabrasive particles are bonded with a conventional grinding wheel bonding agent. Molded into the nonuseable layer 6 are several threaded bolts 8 and washers 10. The wheel 2 is attached to a supporting and driving plate 12 through bolts 14 which pass through holes in plate and are screwed into the threaded nuts 8. The plate 12 l includes a shaft, which is not numbered. The shaft is connected to a motor, either directly or a pulley and belt, which rotates the wheel and plate assembly. The driving force of the plate 12 is conveyed to the wheel solely through the bolts 14 and nuts 8. U.S. Pat. No. 2,836,017 relates to a type of grinding wheel similar to that of U.S. Pat. No. 3,576,090 i.e. a disc wheel. Attachment inserts 3 are molded into the back face of the wheel, each insert comprising a substantially flat web portion 5 including a pair of edge flanges 7 along opposite longitudinal sides of said web portion 5. Both flanges 7 are located on the same side of the plane of web portion 5 and consist of generally perpendicular parts 9 adjacent to the web 5 followed by outwardly inclined parts 11 terminating in the edges 13 which are spaced apart a distance which is greater than the width of the web 5. To facilitate attachment to the driving plate of a grinding machine, the web 5 contains a centrally located hole 15 with a boss 17 on the same side of the web 5 as the flanges 7. Boss 17 is fitted snuggly between the perpendicular parts 9 and for that purpose is provided a pair of parallel edges 19 which are perpendicular to the web 5. Boss 17 includes a threaded opening 21 in registry with the hole 15. It is through the threaded openings and mating bolts that the disc wheel is attached to the driving plate and the entire driving force is imposed on the wheel through the combination of the bolts and attachment element made up of insert 3 molded into the wheel.
U.S. Pat. No.l 4,240,230 to Ferrantini relates to a so-called depressed center wheel in combination with an adapter for attaching the wheel to the shaft of a grinding machine which is usually a portable or hand held grinder. The adapter, which also drives the wheel, is made up of a disc portion 17 which extends axially from a mandrel 11 and has a convex face 19 and a concave face 21. The concave face 21 has a flat flange 23 which extends around the periphery. The flange 23 and ribs 29 make contact with the wheel 25. The flange 23 contains a number of protrusions 27 or bosses which mate with depressions or orifices in the wheel 25. It is the friction between the adapter, and the protrusions 27 on the flange 23 imbedded in the depressions in the wheel 25 that carries the driving force from the grinding machine to the wheel.
Another type of wheel and mounting and driving means is shown in U.S. Pat. No. 4,507,897. In one embodiment of the invention disclosed in the patent a grinding wheel 14, referring to FIGS. 1-5, is molded onto a back plate 11 which has an upper flange 12 and a downwardly directed flange 13. The backing plate 11 has a number of notches 15 in its upper flange 12 which line up with corresponding threaded holes 16 in the outer wall 17 of the back plate holder 18. The back plate 11 is attached to the back plate holder 18 by bolts 19 which pass through the notches 15 and into threaded holes 16. Protruding from the back plate 11 in a downward direction are tabs 21 which are imbedded in the grinding wheel. The tabs transmit the rotation driving force to the grinding wheel 14.